#!/usr/bin/env python3.0

#If we list all the natural numbers below 10 that are multiples of 3 or 5, 
#we get 3, 5, 6 and 9. The sum of these multiples is 23.
#
#Find the sum of all the multiples of 3 or 5 below 1000.

def sumdiv(t, n):
    p = t // n
    return n * p * (p + 1) // 2

if __name__ == '__main__':
    print('Result: ' + str(sumdiv(999, 3) + sumdiv(999, 5) - sumdiv(999, 15)))
    